1. Technical Field
The present invention relates to a camera module in which image pickup elements and an optical component such as a lens are integrally formed.
2. Related Art
In a mobile device such as mobile phone, a model having a built-in camera is now mainstream. A camera mounted in such a mobile device is required to have small size and small thickness. To achieve this, a camera module is being developed, in which an optical component such as a lens and solid image pickup elements such as CMOS sensors are integrally formed.
Recently, the mobile device tends to be reduced in size more and more, and accordingly further size reduction is required for a camera module. To achieve this, each image pickup element itself to be built in the camera module needs to be reduced in size. Thus, it is attempted that the image pickup element is configured by a technique of W-CSP (Wafer-level Chip Size Package) having penetrating electrodes. When the technique is used, wire bonding, which has been used for a camera module in the past, is unnecessary, enabling reduction in size of the camera module.
JP-A No. 2007-036481 discloses a configuration example of a camera module with a built-in W-CSP-type sensor package having image pickup elements. Cover glass is attached to a light-receiving surface of a semiconductor substrate on which the image pickup elements are formed, and plural of solder balls are provided as external connection terminals on a mounting surface. An optical lens, which focuses light from an imaging object onto light-receiving surfaces of the image pickup elements, is provided on a top of the cover glass. A cylindrical lens holder for holding the optical lens is integrally formed with a shading member, which covers the top and side faces of the cover glass so as to shade areas other than a light-receiving area, and combined with the sensor package.
It is considered to be preferable from a viewpoint of achieving small size and low profile that the camera module having a built-in W-CSP-type sensor package is configured such that a lens structure including a lens holder for holding an optical lens, and a shading member for shading a sensor package, is directly joined to the sensor package. In this case, alignment of a relative position of the sensor package to the lens structure is important. That is, it is necessary that an optical distance between the sensor package and the lens should accurately correspond to a focal distance of the lens. In addition, it is necessary that a center of an effective pixel area of the image pickup elements is allowed to correspond to a light axis of the lens. If the lens structure and the sensor package are simply contacted and joined to each other by an adhesive or the like, a relative position between such components may sometimes deviate from an appropriate range due to variation in outside dimension of each component.
In the case that thermosetting resin is used for joining the lens structure to the sensor package, the following problem has occurred: since relatively long time is taken for heat curing, a relative position of the lens structure to the sensor package is hard to be held during heat curing, leading to variation in the relative position. As a measure for this, use of photo-curing resin is considered for joining the lens structure to the sensor package. However, the sensor package is typically covered with a shading member for the lens structure, and therefore a joint of the lens structure to the sensor package is not exposed to the outside. Therefore, the joint is hardly irradiated with light for curing resin, leading to a problem that the photo-curing resin has been hardly used.